We have to classify and analyze digital images for different study and purposes. Digital images are obtained from sources like camera, satellites, aircraft etc. Data obtained from satellites or aircraft i.e, the space based and remote sensing data needs to be corrected as they are usually geometrically distorted due to their acquisition system and the movements of the platform of aircraft. Processing and pre-processing are necessary for such correction prior to image classification. Image Processing is a technique which is used to enhance raw images received from cameras, satellites, space probes, aircrafts etc. and Digital image processing is the technique of processing images in the form of discrete digital brightness using digital circuits or digital computers. Image analysis and classification starts when processing and pre-processing ends.

Bangladesh is one of the disasters prone country faces Cyclones, Floods, draught, Nor'westers/Tornadoes, Thunderstorm Earthquake etc. almost every year. Cyclones are the most devastating storm affecting Bangladesh, but there are other kinds of storm named Nor'westers and Tornadoes. Storms characterized by strong surface wind exceed 100 miles per hour known as tornados. They are formed suddenly, usually on land and are extremely localized. Thunderstorm and Tornado occur in pre-monsoon season frequently in Bangladesh which cause lot destruction to lives and properties and hampers sustainable development. Nor'westers come mainly from the north westerly direction (and hence the name) and are land based. They are a very common phenomenon in Bangladesh during late Chaitra and Baishak month and are known in Bengali as Kalbaishaki. The physical cause of this disaster is embodied in law of science and hence proper scientific research is necessary to deal with them. The Role of Remote Sensing and GIS technology in monitoring of such natural disasters like tornado has been described in this paper.

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In recent years Bangladesh has experienced numerous winter events during the winter. In January 2010, northern and southwest parts of the country experienced a rapid fall in temperature with cold winds and dense fog. In January 2011 the Meteorological Department recorded the temperature as 2 to 5 degrees Celsius lower than the normal average temperature (about 10°C) during that time of the previous year'sresulting significant rise in respiratory illnesses, and in some cases deaths. Some prior arrangement should be made and preparatory measures should be taken by the respective departments, agencies to protect the affected people.Monitoring and prediction prior to the events is thus necessary. Satellite data are very useful for monitoring and analytical study of such natural events and their directional movement. SPARRSO monitors the formation, duration and movement of cold wave as one of its regular activities relating to disaster management, based on data received at its own ground station. In this paper,monitoring of winter events and their analytical study using satellite data will be discussed briefly.

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